Process op and apparatus for recovering the ammonia content of coal gas



B. TORREY, JR

PROCESS OF AND APPARATUS FOR RECOVERING THE AIMMONIA CONTENT OF COAL GAS Filed Nov. 10.

DNI

mvENToR @ma /r BY blo ATToRNl-:Y

@fa/rim Cf. CLJ/LIM@ man@ NNY

Patented Mar. 251i, H524.

UNITED STATES 4PATENT OFFCE.

BATES 'BORR-EY, JR., OF SYRACU'SE, NEVI YORK, ASSIGNOR T0 SEMET-SOLVAY 001V;- PANY, OF SOLVAY, NEVI YORK, A CORSRATION OF NEW YORK.

PROCESS OF AND APPARATUS FOR 2li/"FIJOVERIUQTGr- THE AMMONIA CONTENT OF COAL GAS.

Application filed November 10, 19%.

To @ZZ whom t may concern.'

Be it known that I, BATES Tonner, J r., a citizen of the United States, residing` at Syracuse, in the county of Onondaga and State ot' New York, have invented a new and Improved Process of and Apparatus for Recovering the Ammonia Content of Coal Gas. ot which the following` is a specification.

My invention relates particularly to the treatment of the gas produced by the destructive distillation of coal to the end of recovering its ammonia content, (both that present in the forms of so-called fined and tree ammonia,) in the form of solution or ammoniaca-l liquor. The fixed ammonia is represented by such compounds as choride and sulphate ot ammonia, while the tree ammonia includes the carbonate, sulphide and cyanide.

From such liquor the annnonia is subsequently recovered in commercial form and one object ot my improvements is to obtain a liquor of relatively high ammonia concentration or small volume to the end of economy in the subsequent recovery and utilization of its ammonia content.

This object I accomplish by obtaining at a. single point in the recovery system a iinished liquor which contains both all the fixed and all the free ammonia recovered 'from the gas this point being that point ot the system where is found the best combination of low temperature and high ammonia gas concentration, 'for etlecting ammonia absorption, that is to say, for obtaining a linished liquor o' maximum ammonia content or minimum volume.`

In carrying my invention into effect, the

rater content of the coal which is carried into the hydraulic or gas collecting main as vapor with the gas, is after condensation returned to this part of the system and used to spray the gas in the main whereby tar is removed, the gas cooled and the major portion of the so-called fixed ammonia absorbed. The resulting liquor, after being freed of a substantial portion of its tar content is continuously re-circulated and returned to the main in the form of spray wherewith the gas is washed so that a solution relatively concent ated in lined ammonia is formed.

From this solution, liquor is then drawn off at a rate substantially corresponding to Serial No. 600,032.

the quantity of water being introduced into the main by and condensed from the ga produced by the destructive distillation of the coal so that a uniform quantity of water is maintained in the main.

Further, this 'tined ammonia liquor drawn off from the main and the weak ammonia liquor from the final ammonia scrubbers is used for the final cooling of the gas, by bringing the same in contact therewith after cooling. Thus the absorptive power ot the iixed ammonia liquor and of the weak animonia liquor for free ammonia, is 'further utilized, and this coolingliquor circulation not only cools the gas and removes tar therefrom but also removes a large portion or" the :tree ammonia.

ln this manner the quanti-ty of fresh water required in the recovery of the ammonia content of the gas is lrept" at a minimum and a highly concentrated solution of ammonia is obtained.

The invention will be best understood by reference to the accompanying drawings, Fig. l of which illustrates in diagrammatic form an organization of apparatus which may be used in carrying the invention into effect. Fig. 2 is a view on anenlarged scale, partly in section, of means tor spraying the gas in the hydraulic main, reference being made the-reto by the letters of reference indicating the several parts.

Referring to the drawings, A, indicates a hydraulic or gas collecting main in which the gas from the coal is received as it comes from the retorts (not shown in the drawings), through pipes` X.

Tn this the gas is sprayed with water by well known means, a form of which is shown in Fig. 2. This spraying operation removes much of the tar from the gas and at the same time, theteinperature of the gas lis reduced. A portion of the water Vso used in spraying the gas is carried by the gas in the form of vapor and another portion remains in the main in liquid torni mixed with the tar precipitated from the gas and this liquor contains most of the iXed ammonia originally present in the gas.

The water in the main, together with the tar, is drawn off as through a pipe, l), to a settling tank B where the tar settles out and is drawn off to a tar collect-ing tank (not Obviously, for maximum recovery this fixed ammonia liquor should in no case be introduced into the last ammonia scrubber, K.

It is thus seen that by my process all the finished product is obtained at one point in the system. That this finished product contains substantially all the ammonia of the gas both fixed and free and. that it is of maximum concentration or minimum volume. The cost, therefore., (power, apparatus, heat, etc.) of subsequent handling or working up of this product for concentrated aqua ammonia or any other market product will be less than heretofore.

lt will be noted further that iii-achieving this, the object of my invention, the following steps are taken and intermediate results obtained..

l. All the condensate from the primary cooler is used as make-up water for the hydraulic main, thus supplying all the liquid needed or reducing any fresh water addition to a minimum.

2. A product is obtained from the hydraulic main which is a relatively concentrated solution of fixed ammonia..

This fixed ammonia solution is in turn used to further cool and wash the gas and as an absorbing medium for free ammonia.

if. All the ammonia. liquors of the system are comb-ined and brought into final Contact with the gas at that point in the system where the conditions of low temperature and high ammonia gas concentration are most favorable for ammonia absorption.

5. rlhe load on the ammonia scrubbers is thus reduced effecting a reduction in` their number and in the volume of fresh wat-er used.

Having thus described my invention what l claim as new and desire to secure by Letters Patent is l. The process of recovering ammonia from coal gas which consists in forming a fixed ammonia liquor' by withdrawing liquor from the gas collecting main and continuously returning it to the main and spraying the gas in the main therewith, completing the removal of free ammonia from the gas by scrubbing vthe gas with fresh water and free ammonia liquor formed therefrom, drawing` off a portion of the liquor containing` the fixed ammonia and mixing it with the liquor formed by scrubbing the gas with fresh water and free ammonia liquor formed therefrom, cooling the mixture and washing the gas therewith, and finali;T drawing off1 the resulting ammoniacal liquor Ito storage.

2. The process of recovering the am-4 monia content of coal gas which consists in drawing offl the gas from the gas collecting main and washing and cooling it to effect condensation of its water content, returning the condensate so obtained to the main and spraying the gas therewith to form a fixed ammonia liquor and drawing off a portion of the liquor, mixing the liquors drawn off with liquor containing free ammonia formedL in the final scrubbing of the gas, cooling t-he mixture and washing the gas therewith and finally scrubbing the gas with fresh water and free ammonia liquor formed therefrom to complete the removal of its free ammonia content.

3. The process of recovering the ammonia content of coal gas which consists in drawing off the gas from the gas collecting main and condensing water therefrom and continuously circulating the condensate and spraying the gas in the main therewith so as to effect concentration of the liquor in the main in fixed ammonia, continuously drawing ofl'l a quantity of the concentrated liquor so as to maintain a uniform quantity of wz ter in the main and prevent it from becoming saturated with fixed ammonia, scrubbing the gas with fresh water and free ammonia liquor formed therefrom to effect final removal of the ammonia` therefrom, adding to the liquor derived from such scrubbing the liquor withdrawn from the circulating system carrying the fixed ainmonia, cooling the mixture and washing the gas therewith, and finally drawing ofi' the resulting ammoniacal liquor to storage.

4i. In an organization of apparatus for recovering the ammonia content of coal gas the combination of a collecting gas main and means for spraying the gas therein with water, a circulating system in which gas withdrawn from the main is cooled and its water content condensed and the condensate together with overflow water from the main is returned to the main to spray the gas therein, a scrubbing system in which the gas is scrubbed with fresh water and free ammonia liquor formed therefrom, means for drawing off water charged with fixed arnmonia salts from the said circulating system and for mixing it with the liquor formed by scrubbing the gas with fresh water and free ammonia liquor formed therefrom in t-he scrubbing system and means for cooling the mixture and washing the gas therewith.

The process of recovering ammonia from coal gas which consists in first washing and cooling the gas with water condensate from the gas itself, finally scrubhing the gas with water and free ammonia liquor formed therefrom and intermediate these two operations cooling` and mixing the liquors resulting from the first washing and the final scrubbing, bringing the gas in contact with the mixture and withdrawing the resulting ammoniacal liquor.

6. Tl e process of recovering ammonia from coal gas which is characterized by effecting the final removal of ammonia from the gas by scrubbing the gas with water los) zrnd free ammonia liquor formed therefrom and vprior to suchinel vscrubbing of the gas bringing the gus inkcontect with a cooled liquor containing 4Ehe fixed ammonia, liquor 5 from the gas mein and the Weak .ammonia .15 ished nroducl'nfier its Contact ivirh the gas.

f 8. The process csf recoveringl ammonia fron'rcoul gus .which comprises drawing off the gas from the gas innin and. cooling it so as to remore Wafer vapor therefrom,,spraying .r the gas in the inuin Wih this Water condensate to cool the gus, remove rar and absorb viixed ammonia thereby producing` a. fixed vammonia liquor and prior to the final scrubbing of the ges with Water to remove .1.5 ivhe laseportionso'f ammonia, bringing the ges in Contact Withecooled liquorcontaiir ing `chefixed .ammonia liquor and the Weak ammonia liquor from ythe inal scrubbing.

9. :The `process oli' recovering ammonia from coal gus which comprises drawing; off the ,glas v,from the main, cooling Lit by continuously circulating in Contact with `it Ww ter .condensed from ,the ,ges itself :thereby removing tar and condensing water vVapor therefrom, mixingl Ithe excess condensate with liquor .from the `main and sprnyingthe gas in the main with the mixture whereby turis remoifednnd a fixed ammonia liquor is obtained, linullyremoving ammonia `from the gesby scrubbing,` it Withwater land free nmnionirL liquor formed .therefrom and, prior i'liereto, coolingthegus bybringingit in Contact with cooled liquor from the main and-the iveula: ammonialiquor from the final scrulibing and withdrawing from the System the resultant nmmoniacnl liquor.

ln testimony'whereof I afixmy signature, this (5th day of November, 1922.

BATES i ronREY, JR. 

